| 1. |
- Bakhit, Yousuf, et al.
(author)
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Intrafamilial and interfamilial heterogeneity of PINK1-associated Parkinson's disease in Sudan
- 2023
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In: Parkinsonism & Related Disorders. - : Elsevier. - 1353-8020 .- 1873-5126. ; 111
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Journal article (peer-reviewed)abstract
- PINK1 is the second most predominant gene associated with autosomal recessive Parkinson's disease. Homo-zygous mutations in this gene are associated with an early onset of symptoms. Bradykinesia, tremors, and rigidity are common features, while dystonia, motor fluctuation, and non-motor symptoms occur in a lower percentage of cases and usually respond well to levodopa. We investigated 14 individuals with parkinsonism and eleven symptom-free siblings from three consanguineous Sudanese families, two of them multigenerational, using a custom gene panel screening 34 genes, 27 risk variants, and 8 candidate genes associated with parkinsonism. We found a known pathogenic nonsense PINK1 variant (NM_032409.3:c.1366C>T; p.(Gln456*)), a novel pathogenic single base duplication (NM_032409.3:c.1597dup; p.(Gln533Profs*29)), and another novel pathogenic insertion (NM_032409.3:c.1448_1449ins[1429_1443; TTGAG]; p.(Arg483Serfs*7)). All variants were homozygous and co -segregated in all affected family members. We also identified intrafamilial and interfamilial phenotypic het-erogeneity associated with PINK1 mutations in these Sudanese cases, possibly reflecting the nature of the Sudanese population that has a large effective population size, which suggests a higher possibility of novel findings in monogenic and polygenic diseases in Sudan.
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| 2. |
- Bakhit, Yousuf, et al.
(author)
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PLA2G6-associated late-onset parkinsonism in a Sudanese family
- 2023
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In: Annals of Clinical and Translational Neurology. - : John Wiley & Sons. - 2328-9503. ; 10:6, s. 983-989
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Journal article (peer-reviewed)abstract
- IntroductionThe phospholipase A2 group VI gene (PLA2G6) encodes an enzyme that catalyzes the hydrolytic release of fatty acids from phospholipids. Four neurological disorders with infantile, juvenile, or early adult-onset are associated with PLA2G6 genetic alterations, namely infantile neuroaxonal dystrophy (INAD), atypical neuroaxonal dystrophy (ANAD), dystonia-parkinsonism (DP), and autosomal recessive early-onset parkinsonism (AREP). Few studies in Africa reported PLA2G6-associated disorders and none with parkinsonism of late adult onset.Material and MethodsThe patients were clinically assessed following UK Brain Bank diagnostic criteria and International Parkinson and Movement Disorder Society's Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Brain MRI without contrast was performed. Genetic testing was done using a custom-made Twist panel, screening 34 known genes, 27 risk factors, and 8 candidate genes associated with parkinsonism. Filtered variants were PCR-amplified and validated using Sanger sequencing and also tested in additional family members to study their segregation.ResultTwo siblings born to consanguineous parents developed parkinsonism at the age of 58 and 60 years, respectively. MRI showed an enlarged right hippocampus in patient 2, but no overt abnormalities indicative of INAD or iron deposits. We found two heterozygous variants in PLA2G6, an in-frame deletion NM_003560:c.2070_2072del (p.Val691del) and a missense variant NM_003560:c.956C>T (p.Thr319Met). Both variants were classified as pathogenic.ConclusionThis is the first case in which PLA2G6 is associated with late-onset parkinsonism. Functional analysis is needed to confirm the dual effect of both variants on the structure and function of iPLA2β.
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| 3. |
- Beretta, Chiara, et al.
(author)
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Astrocytes with Alzheimer’s disease pathology provoke lipid droplet mediated cell-to-cell propagation of MHC II complexes
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Other publication (other academic/artistic)abstract
- Background. Astrocytes are critical for maintaining brain homeostasis, but are also highly involved in neuroinflammation. In the Alzheimer disease (AD) brain, reactive, inflammatory astrocytes are situated closely around amyloid β (Aβ) plaques. We have previously shown that reactive astrocytes ingest large quantities of soluble Aβ aggregates, but are unable to degrade the material, which leads to intracellular Aβ accumulation and severe cellular stress. A common response to cellular stress is the formation of lipid droplets (LDs). Novel data indicate that LDs play an important role in inflammatory processes. However, the involvement of LDs in AD inflammation and progression remains unclear.Methods. The aim of this study was to investigate how astrocytic Aβ pathology affects lipid metabolism and antigen presentation. For this purpose, human induced pluripotent stem cell (iPSC) derived astrocytes were exposed to soluble Aβ42 aggregates and analyzed over time, using a battery of experimental approaches.Results. Our results show that Aβ exposure induces LD accumulation in astrocytes, although the overall lipid composition remains unchanged. Moreover, astrocytes transfer LDs to neighboring cells via tunneling nanotubes (TNTs) and extracellular vesicle (EVs). Interestingly, we found that the antigen presenting protein major histocompatibility complex II (MHCII) is present inside LDs, suggesting an active role of LDs in astrocytic antigen presentation. Immunohistochemical analysis of human brain tissue verified the presence of LD-loaded MHCII+ astrocytes in AD individuals. Moreover, we found infiltrated CD4+ T cells to be in close contact with astrocytes, confirming an astrocyte T cell cross-talk in the AD brainConclusions. Taken together, our data show that Aβ pathology drastically affects lipid storage in astrocytes, which in turn modulates the astrocytic antigen presentation, indicating a role for astrocytic LDs in T cell responses in the AD brain.
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| 4. |
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| 5. |
- Eltom, Khalid, et al.
(author)
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Astrocytic accumulation of tau fibrils isolated from Alzheimer’s disease brains induces inflammation, cell-to-cell propagation and neuronal impairment
- 2024
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In: Acta neuropathologica communications. - : BioMed Central (BMC). - 2051-5960. ; 12:1
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Journal article (peer-reviewed)abstract
- Accumulating evidence highlights the involvement of astrocytes in Alzheimer’s disease (AD) progression. We have previously demonstrated that human iPSC-derived astrocytes ingest and modify synthetic tau fibrils in a way that enhances their seeding efficiency. However, synthetic tau fibrils differ significantly from in vivo formed fibrils. To mimic the situation in the brain, we here analyzed astrocytes’ processing of human brain-derived tau fibrils and its consequences for cellular physiology. Tau fibrils were extracted from both AD and control brains, aiming to examine any potential differences in astrocyte response depending on the origin of fibrils. Our results show that human astrocytes internalize, but fail to degrade, both AD and control tau fibrils. Instead, pathogenic, seeding capable tau proteoforms are spread to surrounding cells via tunneling nanotubes and exocytosis. Notably, accumulation of AD tau fibrils induces a stronger reactive state in astrocytes, compared to control fibrils, evident by the augmented expression of vimentin and GFAP, as well as by an increased secretion of the pro-inflammatory cytokines IL-8 and MCP-1. Moreover, conditioned media from astrocytes with AD tau fibril deposits induce synapse and metabolic impairment in human iPSC-derived neurons. Taken together, our data suggest that the accumulation of brain-derived AD tau fibrils induces a more robust inflammatory and neurotoxic phenotype in human astrocytes, accentuating the nature of tau fibrils as an important contributing factor to inflammation and neurodegeneration in AD.
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| 6. |
- Mothes, Tobias, et al.
(author)
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APOEε2 drives tau processing and tau-mediated inflammation in human iPSC derived astrocytes
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Other publication (other academic/artistic)abstract
- Background: Alzheimer’s disease (AD) and progressive supra-nuclear palsy (PSP) are both proteinopathies, characterized by accumulation of tau aggregates. APOEε4 is the greatest genetic risk factor for developing AD, while APOEε2 constitutes a decreased risk. On the contrary, APOEε2 is a significant risk factor for developing PSP. In the brain, astrocytes are the predominant producer of ApoE, but they are also important for synapse function, inflammation and overall brain homeostasis. Although, tau inclusions appear frequently in astrocytes in both AD and PSP brains, their connection to ApoE remains unclear. Methods: The aim of this study was to investigate how the APOEε-genotype influences astrocytes’ accumulation, processing and spreading of pathogenic tau aggregates, as well as their inflammatory status and neuronal support. For this purpose, we exposed isogenic hiPSC-derived APOE 2/2 and APOE 4/4 astrocytes to synthetic tau fibrils (Tau-F). Intracellular tau processing was analysed with immunocytochemistry and western blot, while secreted tau was analysed with ELISA. Cytokine levels in astrocyte conditioned medium (ACM) were measured with MesoScale analysis and seeding efficiency was examined using the Tau RD P301S FRET Biosensor and a close-culture chamber. Lastly, we exposed iPSC derived neurons to ACM from tau exposed astrocytes of both genotypes to assess potential neurotoxic effects.Results: Exposure to Tau-F resulted in more and larger intracellular tau-deposits in APOE 2/2 astrocytes, compared to APOE 4/4 astrocytes, while the tau levels in ACM remained similar. Western blot analysis demonstrated that the processing of internalized tau was clearly different between the genotypes. Moreover, APOE 2/2 was the dominant driver of inflammation with higher secreted levels of IL-8, CXCL10 and CCL2. The ApoE genotype did not influence neuronal health or direct seeding capacity of excreted tau. However, Tau-F had a 3-fold higher seeding efficiency when diluted in ACM from APOE 2/2 astrocytes, compared to APOE 4/4 astrocytes. Conclusions: Our results show that APOE 2/2 astrocytes accumulate, process and spread pathogenic tau aggregates more efficiently than APOE 4/4 astrocytes, highlighting a role of ApoE in astrocyte-mediated tau pathology. Moreover, the APOE 2/2 astrocytes display a more robust inflammatory response, which could be of relevance for the disease course.
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| 7. |
- Mothes, Tobias, et al.
(author)
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Astrocytic uptake of neuronal corpses promotes cell-to-cell spreading of tau pathology
- 2023
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In: Acta neuropathologica communications. - : BioMed Central (BMC). - 2051-5960. ; 11:1
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Journal article (peer-reviewed)abstract
- Tau deposits in astrocytes are frequently found in Alzheimer's disease (AD) and other tauopathies. Since astrocytes do not express tau, the inclusions have been suggested to be of neuronal origin. However, the mechanisms behind their appearance and their relevance for disease progression remain unknown. Here we demonstrate, using a battery of experimental techniques that human astrocytes serve as an intermediator, promoting cell-to-cell spreading of pathological tau. Human astrocytes engulf and process, but fail to fully degrade dead neurons with tau pathology, as well as synthetic tau fibrils and tau aggregates isolated from AD brain tissue. Instead, the pathogenic tau is spread to nearby cells via secretion and tunneling nanotube mediated transfer. By performing co-culture experiments we could show that tau-containing astrocytes induce tau pathology in healthy human neurons directly. Furthermore, our results from a FRET based seeding assay, demonstrated that the tau proteoforms secreted by astrocytes have an exceptional seeding capacity, compared to the original tau species engulfed by the cells. Taken together, our study establishes a central role for astrocytes in mediating tau pathology, which could be of relevance for identifying novel treatment targets for AD and other tauopathies.
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| 8. |
- Mothes, Tobias, et al.
(author)
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Spreading and morphology of α-synuclein, amyloid-β and tau deposits in cortical organoids
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Other publication (other academic/artistic)abstract
- Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the two most common neurodegenerative diseases, both defined by accumulation of aggregated proteins. In the AD brain, amyloid-beta (Aβ) and tau form the characteristic plaques and tangles, while alpha-synuclein (αSYN) form Lewy body inclusions in the PD brain. In addition, deposits of tau, Aβ and αSYN appear frequently in astrocytes. The pathological protein aggregates are known to propagate throughout the brain in a prion-like manner, resulting in cognitive and functional impairments. However, the exact cellular mechanisms behind the spreading remain elusive. As previous propagation studies in AD and PD mouse models fail to resemble the human brain biology, we here developed a human cerebral organoid system, suitable for studying early spreading events of tau, Aβ and αSYN proteins. Using this system, we analyzed the propagation patterns of αSYN, Aβ and tau aggregates, when added directly to the organoids or when introduced through co-incubation with human astrocytes previously exposed to these protein aggregates. Following exposure, the organoids were cultured for one or four weeks prior to analysis. Our results demonstrate that all aggregates, both when added directly and within astrocytes, penetrate the organoids. However, the three aggregates showed significant differences in inclusion morphology and overall distribution. Taken together, we present highly relevant and replicable AD/PD models to study early spreading events of pathological proteins.
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